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11/27/06
Headtube Innards
Filed under: bike tech, cyclocross
Posted by: The Cyclofiend @ 10:39 am

Rainy Sunday put me out in the garage, stripping the bits off of the Poprad to see what the inside of the headtube looked like.  During the teardown, the four-thumbed and no-brained mechanic made an appearance, which ended up with a few chainring bites on the knuckles and two vaporized self-removing crankbolt caps.  (One would’ve been a hardware failure, but plunging ahead to muscle the second one showed a hopefully rare lack of thought…)

By the time things were off and boxed, I took some inside the headtube photos which correspond to outwardlyl visible cracks mentioned in this post.  Click on them to see larger versions.

We’ll start off with a general view up from the bottom of the headtube.  The open holes are where the downtube (nearest) and headtube are joined.  As a technical aside, this is a TIG-welded frame, using Reynolds 853.

I’m guessing that the circle of beading is normal.  The next view shows what appears to be a crack out from the hole through the weld bead, at what would be “4 o’clock”.  This seems to line up with the visible crack on the outside.

Another shot, looking for the crack at “7 o’clock”.   Seems to be one there in a similar fashion.  In the larger photo, it’s not as visible, as the macro focus range grabbed just beyond the crack.  With the low depth of field, it’s a bit soft.  I was lighting these with a little 4 LED headlamp from the other end fo the tube, with some available light coming through a window behind me (on an overcast and rainy day).

Now we move to the top of the headtube.  This one is a bit less obvious, so I’ve provided both a regular and outlined version.

Well, that’s kinda the news for now.  I’m hoping to get a bit of time in the afternoon to go show it to the folks at the bike shop, and see what’s next.

10 Responses to “Headtube Innards”

  1. Jim G Says:
    I really didn’t think there’d be anything to see inside the headtube, but wow…that’s pretty compelling evidence! You should post this on the Framebuilders’ list just to get their perspective…
  2. The Cyclofiend Says:
    I’ll try to do that later today - Right now, it’s with the fine folks at the LBS. The Service Manager is supposed to be addressing the issue & will be getting back to me. I emailed him the same set of photos, so it will be interesting to see the response. The wrench at the counter did allow as how they don’t make them out of the “good tubes” anymore…
  3. Tarik Saleh Says:
    OK, thats just weird. I was thinking tiny cracks in the crappyweld. I would not really have thought that the cracks would have gone into the HT like that. I would have guessed that they would have gone through the dt, or through the rest of the weld. Or at least onto the outside of the ht. I am interested to see the feedback on the framebuilders list. I wonder if it started from a really shitty miter on the inside of the tube, weird…
  4. Tarik Saleh Says:
    “shitty miter on the inside of the tube,” I meant a shitty drilled hole in the HT
  5. The Cyclofiend Says:
    Got 4 or 5 thoughtful responses from the gang on the framebuilders list - Thanks JimG! - I’ll probably post a few of them when I have a moment.
  6. The Cyclofiend Says:
    It’s hard to see from the photos, but the two bottom cracks are on almost identical locations on their respective sides (bilateral symmetry). Seems like something was flexing for some reason, but I’m really outside of my knowledge area on that.
  7. Jim G Says:
    Wow!

    “Jim, I’ve seen that several times, mostly on titanium frames, but also on steel. The cause seems to be… ” (click for full text)
  8. The Cyclofiend Says:
    That was the most specific comment I’ve received. It’s been interesting to hear the feedback from the folks on the Framebuilders’ List. Thanks again for pointing me their direction.
  9. Jim Bailey Says:
    Hi Jim, I’ve followed your clips about the cracks in your Poprad. I own one and am curious about the final resolution between LeMond Bikes and you. How’d it turn out?
  10. The Cyclofiend Says:
    Hey there Jim - It actually has turned out reasonably trouble-free.



    The LBS quickly received a replacement frame which I now have and we are currently waiting for an appropriate fork. More photos here and a follow-up post here.